A tik tik sound from the middle under the vehicle. on 2001 Mercedes-Benz C240

Tik tik sound goes faster and slower as the car picks up speed or lower speed.The sound does not happen all the time.When the car is could the noise is quiet.

Asked by for the 2001 Mercedes-Benz C240
how long since last oil change?
No Idea If Gearbox Oil has ever been changed.The car has done 159000 Km